title: Anisotropic dry adhesive via cap defects.
abstract: We demonstrate how introducing a deliberate defect on the overhanging caps of strongly adhering mushroom shaped dry adhesive fibers can produce directional adhesion behavior. We find that the shape and location of this defect controls both the total adhesion force and the degree of directionality for these bio-inspired adhesives. Linear beam theory is used to demonstrate how the application of a shear load to a fiber in tension can create a small compressive load to an asymmetric crack, thereby delaying adhesion failure and producing directional adhesion, and the theory is confirmed with finite element models and empirical data. Anisotropic adhesives have been fabricated and tested and can demonstrate normal adhesion force up to ~250 kPa with a shear displacement of 15 µm away from the defect and as small as ~5 kPa when sheared the same amount towards the defect.
authors.affiliation: Department of Mechanical Engineering, University of Alberta, Edmonton, AB T6G2G8, Canada.
authors.forename: Walid Bin
authors.initials: WB
authors.lastname: Khaled
authors.forename: Dan
authors.initials: D
authors.lastname: Sameoto
mesh_terms: D000268:Adhesiveness; D000269:Adhesives / Q000737:chemistry*; D000818:Animals; D016880:Anisotropy; D040761:Biomimetic Materials / Q000737:chemistry*; D003198:Computer Simulation; D006244:Hardness; D008116:Lizards / Q000502:physiology*; D008422:Materials Testing; D008956:Models, Chemical; D033081:Shear Strength; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: D000269:Adhesives